Variable width pulse gate generator



July 14, 1964 w. L. GATES ETAL 3,141,143

VARIABLE WIDTH PULSE GATE GENERATOR Filed Oct. 19, 1960 OUTPUT 33 GATE INPUT TRIGGER FIg.l.

OUTPUT GATE w VARIABLE l AMPLITUDE INPUT WIDTH CONTROL SIGNAL Fig.2.

INPUT TRIGGER 20 -250 W|TNESSES= INVENTORS WiHium L. Gu'Ies 0nd Curl J. Schubert,Jr. W/ W ATTORNEY United States Patent VARIABLE WIDTH PULSE GATE GENERATOR William L. Gates, Takoma Park, and Carl J. Schubert, Jr.,

Arbutus, Md., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 19, 1960, Ser. No. 63,682 12 Claims. (Cl. 332-9) This invention relates to improvements in gate generators, and more particularly to an improved gate generator having a fast rise and a linearly variable gate width.

A primary object of the instant invention is to provide a new and improved gate generator.

Another object of the invention is to provide a new and improved gate generator in which the width of the output gate can be varied in accordance with variations in a direct current voltage.

A further object is to provide a fast rise gate generator in which the output gate width may be continuously and linearly variable over the range of gate widths of the circuit.

A further object is to provide a gate generator capable of operating over a Wide range of input trigger repetition frequencies and output duty cycles.

Still a further object is to provide a new and improved gate generator circuit employing a single tube with a high figure of merit thereby permitting a fast rise time of an output gate and a high amplitude output gate.

A further object is to provide a gate generator circuit which can be operated over a wide range of input trigger widths and amplitudes.

These and other objects will become more clearly apparent after a study of the following specification when read in connection with the accompanying drawing, in which:

FIGURE 1 is a simplified schematic electrical circuit diagram of the tube connections for describing-in detail the tube operation of the secondary emission tube employed in this invention; and

FIG. 2 is a schematic electrical circuit diagram of the preferred embodiment of the invention.

Referring to the drawings in which like reference numerals are used throughout to designate like parts for a more detailed understanding of the invention, and in particular to FIG. 1 thereof, there is shown generally designated 10 a secondary emission tube which may be of a type known in the trade as a 5857. A basic discussion of the theory of operation of secondary emission tubes appears in an article entitled How To Use the Secondary Emission Pentode in Electronics, October 7, 1960, pp. 6063, and other articles referenced therein. The tube 10 is seen to have a cathode 11, control grid 12, screen grid 13, a third grid or suppressor 14, a shield or accelerating element or electrode 15, dynode 16 and anode 17. Cathode 11 is connected by Way of lead 18 and rectifier 19 to ground 20, and lead 18 is also connected to the aforementioned grid or suppressor 14. Lead 18 is also connected by way of capacitor 21 to receive a trigger from an input trigger generator 22 of any convenient design. The aforementioned control grid 12 is connected by way of lead 24 and resistor 25 to the negative terminal 26 of a suitable source of biasing potential, not shown, having the other positive terminal thereof connected to ground 20. Lead 24 is also connected by way of coupling capacitor 27, lead 28 and resistor 29 to the positive terminal 30 of a suitable source of direct current potential, not shown, of the order of 200 volts having the other negative terminal thereof connected to ground 20. Lead 28 is also connected to the aforementioned dynode 16 as shown. The aforementioned screen grid 13 is connected by way of lead 33 to positive terminal 23 of a suitable source of direct ice current potential of the order of volts, not shown, having the other negative terminal thereof connected to ground 20. The aforementioned accelerating electrode 15 is connected by lead 31 to the positive terminal 32 of a suitable source of direct current potential of the order of 250 volts, not shown, having the other negative terminal thereof connected to ground 20. The aforementioned anode 17 is connected by way of lead 35 and resistor 36 to the positive terminal 37 of a suitable source of direct current potential of the order of 300 volts, not shown, having the other negative termial thereof connected to ground 20. Lead 35 is also connected to an output utilization device shown in block form at 38 and being of any convenient design. Any suitable source, not shown, may be employed for heating the heater 9.

In the operation of the circuit of FIG. 1, an input trigger of negative polarity with respect to ground is applied through capacitor 21 to the cathode 11 of the secondary emission tube generally designated 10. Prior to the application of this trigger, the tube is in a non-conducting state due to the presence of the negative bias at terminal 26 applied to the control grid 12. Upon application of the negative input trigger to the cathode 11, conduction through the tube from cathode to dynode 16 commences. At the dynode, secondary emission takes place and an amplified electron flow is initiated between the dynode 16 and the anode 17. The loss of electrons makes dynode 16 more positive. The current flow develops a positive pulse across resistor 29 which is coupled through capacitor 27 to the control grid 12, driving the tube into saturation. At the same time, an output gate is developed across resistor 36 where the current flow to the dynode and cathode produces a negative pulse. Cathode current is maintained during a time interval due to the positive voltage on the control grid of the tube, and this current is applied from the power source connected between ground and terminal 37 and flows through the low resistance of the diode 19 in the cathode circuit. The duration of this interval is determined by the time constant of the circuit through which capacitor 27 charges. As capacitor 27 is charging toward the amplitude of the positive pulse on the dynode 16, the positive voltage on the control grid of the tube decreases. Finally, the control grid voltage drops to a low enough potential to cause conduction to be cut off, and the circuit returns to its original condition, as in the similar case of a monostable multivibrator of conventional design. When the conduction through the dynode 16 drops, the positive pulse across resistor 29 ends, and the voltage drops back to its former +200 volt level. Since capacitor 27 has been charging during the pulse interval, it must now discharge to its original state. The discharge produces a negative pulse across resistor 25 which drives the tube rapidly into cutoff producing the fast fall time of the output gate. The discharge time of capacitor 27 is kept short so that the recovery time of the circuit will not interfere with its operation at higher trigger repetition rates.

It is a characteristic of the above described circuit of FIG. 1 that the gate generator is relatively insensitive to variations in the input trigger width and amplitude. When the leading edge of the negative input trigger is coupled to the cathode of the secondary emission tube, conduction is initiated at once. The input trigger is then differentiated by the R-C circuit composed of the coupling capacitor 21, load resistor 36 and the plate resistance of the tube. Therefore, only the initial negative spike appears at the cathode. At the end of the input trigger pulse a positive spike would appear at this point. However, the diode 19 limits this spike, preventing it from interfering with the operation of the gate generator. In the circuit of FIG. 1, the pulse width could be changed by mechanical switching or relaying to change the value of the capacitor 27 or the value of resistor 25 in the feedback circuit.

Particular reference is made now to FIG. 2, which shows a schematic electrical circuit diagram of the preferred embodiment of the invention. In FIGURE 2, the cathode 11 is connected by way of lead 18 to the aforementioned suppressor 14 of the secondary emission tube 10. Lead 18 is connected by way of capacitor 43 and lead 44 to receive the trigger from the input trigger generator 22. Lead 18 is connected by way of diode 45, lead 46 and the resistor 47 to ground 20. Resistor 47 has capacitor 43 connected in shunt therewith, and lead 46 is also connected by way of potentiometer 49 and resistor 50 to terminal 51 which is the negative terminal of a suitable source of potential, not shown, of the order of 250 volts having the other positive terminal thereof connected to ground 20. The arm 54 of potentiometer 49 is connected by way of resistor 55, lead 56 and resistor 57 to the aforementioned control grid 12. Lead 56 is also connected by way of capacitor 53, lead 59, inductor 60 and resistor 61 to the positive terminal 62 of a suitable source of direct current potential, not shown, of the order of 150 volts with respect to ground 20. Lead 59 is also connected to the aforementioned dynode element 16.

The anode 17 of tube is connected by way of lead 65 to the output gate utilization circuit 38, and the anode is also connected by way of lead 65 and resistor 66 to a terminal 67 which is connected to the positive terminal of a suitable source of direct current potential of the order of 250 volts, not shown, having the negative terminal thereof connected to ground 20.

The aforementioned accelerating electrode is connected by way of lead 68 and resistor 69 to a terminal '70 which is connected to the positive terminal of a suitable source of direct current potential of the order of 250 volts, not shown, having the other negative terminal connected to ground 20. Lead 68 has capacitor 71 connected therefrom to ground and also has resistor 72 connected therefrom to ground, a providing a voltage divider, so that the amplitude of the voltage on accelerator 15 is a predetermined portion of the amplitude of the voltage at terminal 70.

The aforementioned screen grid 13 of the secondary emission tube 10 is connected by way of lead 75 and capacitor 76 to receive the output variable amplitude width control signal generated by the apparatus, of any convenient design, shown in block form at 77, which may provide a recurrent sweep type output. This width control potential is adjustable Within the range wherein the screen grid voltage controls the cathode-to-control grid resistance of the tube. Lead 75 has capacitor 78 connected therefrom to ground 20. Lead 75 also is connected to ground by way of a circuit including the rectifier 79, lead 80 and potentiometer 81. The arm 82 of the potentiometer 81 is connected to the aforementioned lead 80. Lead 80 is also connected by way of the resistor 85 to lead 75, and lead 80 is further connected by way of resistor 83 to terminal 84 which is connected to the negative terminal of a suitable source of direct current potential of the order of 250 volts, not shown, having the other positive terminal thereof connected to ground 20.

In the operation of the circuit of FIGURE 2, there is disclosed circuitry to enable the width of the output gate to be varied continuously and linearly by an input width control potential on lead 74, such for example as that obtained from the output of a function generator. The duration of the tube conduction interval or the output gate width is determined by the charging time of the feedback coupling capacitor 58. This charging time constant is determined by the value of the capacitance and the series resistance which includes resistor 55 in parallel with the cathode-to-control grid resistance of the tube in the saturation condition, the dynode to anode resistance of the tube, and the plate load resistor 66. The circuit utilizes the dependence of the cathode to control grid resistance of the saturated secondary emission tube upon its screen grid voltage to obtain the desired variation in the output gate width. When the resistance 55 is much greater than this interelectrode resistance, the resistance in the charging path of capacitor 58 is a linear function of the screen grid voltage over a fairly wide range of voltages thereby permitting a wide variation in gate width. Under these conditions, when the screen grid voltage is made more positive, electrons emitted from the cathode are accelerated to a higher velocity as they pass the control grid. Fewer electrons are collected by the control grid therefore, and the saturated cathode-to'control grid resistance of the tube is increased. This results in a longer charging time for capacitor 58 and a longer output gate Width. Similarly, when the screen grid is made less positive, the output gate width is decreased.

The sensitivity of the circuit to input trigger amplitude is relatively unaffected since the bias on the tube is not changed by the gate width control voltage. The range of linear operation of the circuit is extended by proper selection of inductance 60 inserted in series with the dynode load resistor 61. A direct current restorer circuit comprising capacitor 76, resistor 85 and rectifier 79 is connected to the screen grid so that the input signal is clamped at the desired level at the start of each sweep of the width control voltage.

By the use of 'a direct current potential source whose output is variable or adjustable within the permissible range of screen grid potentials this clamping circuit can be eliminated thereby permitting direct coupling between the screen grid 13 and the width control signal source 77.

The circuit has been found to be suitable for trigger amplitudes between 3 and 20 volts at recurrence frequencies between cycles per second and 100 kilocycles per second utilizing component values as follows:

Resistors:

47 10 kilohms. 49 1K. 50 39K 55 5.1K 57 33 ohms 61 270 ohms 66 470 ohms 69 51K 72 200K 81 10K 85 l megohm. 83 K. Capacitors:

43 39 mrnf. 48 0.47 mf. 58 510 mrnf. 71 0.47 mf. 76 10 mf. 78 0.47 mf. Diode:

45 1N270. 79 1N643. Inductor 60 22 microhenries.

The output gate may have an amplitude of 15 volts with a 20 millimicrosecond rise time. The gate width is linearly variable between .03 microsecond at 45 volts screen grid voltage and 0.25 microsecond at l9 volts screen grid voltage, with the cathode at -50 volts, so that, in effect, the screen grid potential with respect to cathode varied from approximately a positive 5 to a positive 31 volts.

In summary, the invention includes a normally nonconductive secondary emission tube triggered into conduction by a trigger applied to the cathode, and having capacitor coupled feedback from the dynode to the control grid to cause the tube to become saturated for a time .dynode and anode, a source of a direct current width control potential of uniform polarity and of variable amplitude, circuit means connecting said source to said screen grid for varying the direct current potential on the screen grid, a source of anode potential of predetermined amplitude, a first resistor, a rectifier, said anode, said first resistor, said source of anode potential, said rectifier and said cathode being in series circuit relationship, output lead means connected to said anode, a source of trigger pulses of predetermined amplitude and polarity, further circuit means connecting said last-named source to said cathode, a source of dynode potential, means including a second resistor connecting said source of dynode potential to said dynode, a feedback capacitor operatively connecting said dynode to said control grid, a source of control grid biasing potential, and means including a third resistor connecting said source of biasing potential to said control grid, said secondary emission tube normally in the absence of an input trigger applied to said cathode being biased at cut-off by the biasing potential applied to the control grid, a trigger pulse of predetermined polarity applied to said cathode initiating electron flow in said secondary emission tube from said cathode to said dynode, secondary emission from the dynode to the anode consisting of a larger number of electrons than reach said dynode from said cathode whereby said dynode assumes an increased positive potential, said increased positive potential being applied through said feedback capacitor to said control grid, the electron flow from said dynode and cathode to said anode causing a current flow in said first resistor thereby reducing the potential on said anode and causing an output gate pulse of negative polarity on the output lead means, said third resistor in said control grid circuit being selected in value in accordance with the interelectrode resistance between the cathode and control grid of said secondary emission tube whereby said third resistor is substantially greater than said interelectrode resistance thereby providing that the resistance in the charging path of said feedback capacitor is a linear function of the direct current potential on the screen grid, an increase in the positive direct current potential on the screen grid with respect to the cathode accelerating electrons which pass the control grid to a higher velocity whereby fewer electrons are collected by the control grid and the saturated cathode-to-control-grid resistance of the secondary emission tube is increased resulting in a longer charging time for the feedback capacitor and a Wider output gate width, a decrease in said direct current potential on the screen grid resulting in a narrower output gate Width.

2. A gate generator for generating a gate of variable Width comprising, in combination, a secondary emission tube having at least a cathode, control grid, screen grid, dynode and anode, a source of anode energizing potential, a first resistor, a rectifier, said anode, said first resistor, said source of anode potential, said rectifier and said cathode being in series circuit relationship, output lead means connected to said anode, a source of dynode potential, a second resistor connecting said dynode to said source of dynode potential, a feedback capacitor operatively connecting said dynode to said control grid, a source of biasing potential for said control grid, means including a third resistor operatively connecting the source of biasing potential to said control grid, the charging path of said feedback capacitor being through said third resistor, means connected to the screen grid for applying a source of direct current potential of predetermined polarity and of adjustable amplitude to said screen grid, and means connected to said cathode for applying an input trigger of predetermined polarity to the cathode, said secondary emission tube being normally biased to a cut-off condition by the source of biasing potential, said input trigger applied to said cathode initiating conduction in said secondary emission tube, electrons being attracted from said cathode to said dynode and causing the emission of a larger number of electrons from the dynode to the anode, the current flow to said anode causing said anode to fall in potential and produce a negative output pulse on said output lead means, the flow of a larger number of electrons from said dynode than are received by said dynode causing said dynode to assume a more positive Potential, said positive potential on the dynode being coupled through said feedback capacitor to said control grid, the voltage on the control grid maintaining cathode current through the secondary emission tube for a predetermined time interval, said third resistor being effectively in shunt with the internal cathode-to-control grid impedance of the tube, a variation in the voltage on said screen grid varying the internal cathode-to-control grid impedance thereby varying the total effective resistance in the charging path of said feedback capacitor and varying the charging time of said feedback capacitor, variations in the charging time of the feedback capacitor varying the width of the output pulse on the output lead means.

3. A gate generator for generating a gate of adjustable Width comprising, in combination, a secondary emission tube having at least a cathode, control grid, screen grid, dynode and anode, circuit means including anode load means and a plurality of energizing and biasing potentials connected to said control grid, screen grid, dynode and anode, output lead means connected to said anode and having the output gate pulse developed thereon, one of said sources of energizing potential being operatively connected to said dynode and maintaining said dynode normally at a positive potential less than said anode, means connected to said circuit means for applying a trigger of negative polarity to said cathode, means connected to the circuit means for applying a direct current control potential of positive polarity with respect to the cathode and adjustable amplitude to said screen grid, means including resistance means connected to the control grid for applying a negative direct current biasing potential of adjustable amplitude to the control grid, and feedback capacitor means connecting said dynode to said control grid, the charging path of said feedback capacitor means being through said resistance means, said resistance means being effectively in parallel with the internal cathode-to-control grid impedance in the secondary emission tube, said secondary emission tube being normally biased at cut-off, the negative trigger applied to said cathode initiating conduction in said secondary emission tube, conduction in said tube resulting in an increase in the positive potential on said dynode, said last-named positive potential being coupled through said feedback capacitor means to said control grid and maintaining said control grid at a positive potential sufiicient to maintain conduction in said secondary emission tube for a predetermined period of time in accordance with the charging time of said feedback capacitor means, variations in the amplitude of the control potential applied to the screen grid varying the internal cathode-to-control grid impedance of the tube thereby varying the resistance in the charging path of said feedback capacitor means and varying the charging time of said feedback capacitor means and accordingly varying the width of the output pulses.

4. A gate generator for generating a gate of variable width comprising, in combination, a secondary emission tube having at least a cathode, control grid, screen grid,

dynode and anode, output lead means connected to said anode, a source of anode potential, a source of dynode potential, a source of control grid biasing potential, circuit means including resistance means connecting the source of anode potential, source of dynode potential, and source of control grid biasing potential to said secondary emission tube, a rectifier in said circuit means in the cathode current path of said secondary emission tube, a coupling capacitor connecting the dynode to the control grid, a portion of said resistance means being in the charging path of said coupling capacitor, means connected to the cathode for applying a negative trigger thereto, and a source of direct current potential of adjustable amplitude operatively connected to said screen grid, said secondary emission tube being normally biased at cut-off, the negative trigger applied to said cathode initiating conduction in said secondary emission tube, the flow of electrons from said cathode to said dynode resulting in a greater flow of electrons from the dynode to said anode, said greater flow of electrons causing said dynode to assume an increased positive potential, said increased positive potential being coupled through said capacitor to said control grid, the voltage on said control grid from said capacitor maintaining said tube in conduction for a predetermined period of time in accordance with charge on said capacitor, the said portion of said resistance means being effectively in parallel with the internal cathode-to-control grid impedance of the secondary emission tube whereby the charging time of the capacitor is jointly controlled by said internal impedance and said portion of said resistance means, the internal impedance being under the control of the direct current voltage on said screen grid, the anode current causing the appearance of an output pulse on said output lead means.

5. A gate generator for generating a gate pulse of variable width comprising, in combination, a secondary emission tube having a cathode, control grid, screen grid, suppressor, dynode and anode, output circuit means connected to said anode, said suppressor being directly connected to said cathode, circuit means including impedance means and a plurality of sources of biasing potentials connected to said cathode, control grid, screen grid, suppressor, dynode and anode, the value of said impedance means being selected in accordance with the saturated cathode-to-control grid internal impedance of the secondary emission tube, feedback means connected to the secondary emission tube for feeding back a voltage from the dynode to the control grid thereof, means for applying a trigger voltage of predetermined polarity to said cathode, and means for applying a gate width control voltage to said screen grid, said control voltage varying the time interval of said feedback means in accordance with variations in the amplitude of the control voltage, said feedback means thereby controlling the time interval of the flow of conduction in said secondary emission tube in accordance with the value of said internal impedance and thereby controlling the width of the gate pulse.

6. A gate generator for generating a gate of variable width comprising, in combination, a secondary emission tube having a plurality of electrodes including at least a cathode, control grid, screen grid, dynode and anode means connected to said electrodes for respectively biasing said electrodes, output circuit means connected to said anode, trigger circuit means connected to said cathode, variable control voltage means connected to said screen grid, coupling means connecting the dynode to the control grid, said secondary emission tube being normally biased at cut-01f, a trigger signal from said trigger circuit means applied to said cathode initiating conduction in said secondary emission tube, the flow of electrons in said secondary emission tube causing said dynode to change in potential, said change in dynode potential being coupled through the coupling means to said control grid causing a saturated condition in said tube, said secondary emission tube having a predetermined saturated internal cathode-tocontrol grid impedance, said coupling means having a predetermined time constant under the control of said internal impedance, said internal impedance being variable in accordance with the voltage on the screen grid, the potential on the coupling means in accordance with said time constant maintaining conduction in said secondary emission tube for a predetermined time interval thereby providing an output gate pulse of predetermined duration.

7. A gate generator for generating a gate of variable width comprising, in combination, a secondary emission tube having a plurality of electrodes including at least a cathode, control grid, screen grid, dynode, and anode, means connected to said electrodes for respectively biasing said electrodes, said secondary emission tube having a predetermined saturated internal cathode-to-control grid impedance, output means connected to one of said electrodes to derive an output signal therefrom, the width of the gate pulses in the output means corresponding to the time interval during which the secondary emission tube is conductive, circuit means including a coupling capacitor connected between said dynode and control grid, said circuit means including resistance means in the charging path of said capacitor, said resistance means being effectively in shunt with said internal impedance, the charging time of said capacitor being a function of the total impedance of the resistance means and said internal impedance, the charging time of said capacitor controlling the gate pulse width, and means for applying a variable direct current potential to said screen grid for adjusting said internal impedance and thereby said charging time interval to thereby vary the width of the output gate pulse.

8. A gate generator for generating a gate of variable Width comprising, in combination, a secondary emission tube having a plurality of electrodes including at least a cathode, control grid, screen grid, dynode, and anode, output circuit means connected to one of said electrodes, other circuit means including feedback means connected between said dynode and said control grid and a plurality of sources of energizing and biasing potentials connected to said electrodes, means connected to the secondary emission tube for applying a trigger pulse of predetermined polarity to the cathode thereof to initiate conduction in the tube, means for applying a direct current potential of adjustable amplitude to said screen grid to vary the cathode to control grid impedance of said tube, said other circuit means being operative with said internal cathode-to-control grid impedance of the secondary emission tube to control the time of conduction of said tube and thereby control the Width of the gate generated at said output means.

9. A gate generator for generating a gate of variable Width comprising, in combination, a secondary emission tube having a plurality of electrodes including at least a cathode, screen grid, control grid, dynode and anode, circuit means connected to the anode for obtaining output gate pulses therefrom, other circuit means including a charging path and a plurality of sources of direct current potential for supplying energizing and biasing potentials to said electrodes, means in said charging path for feeding back a voltage developed on said dynode resulting from the emission of electrons therefrom to said control grid to apply a positive voltage to said control grid, means for applying a trigger to said cathode to initiate conduction in said tube, and means for applying a variable direct current control voltage of adjustable amplitude to said screen grid, said charging path arranged to utilize the direct current potential on the screen grid in accordance with the internal cathode-to-control grid impedance of the secondary emission tube to vary the time interval during which the secondary emission tube is conductive and thereby vary the Width of the output gate pulses.

10. A gate generator for generating a gate of variable width comprising, in combination, a secondary emission tube comprising a cathode, control grid, screen grid, suppressor, accelerating electrode, dynode and anode, output circuit means connected to the anode, a first source of potential connected to said dynode for normally maintaining said dynode at a first predetermined positive potential with respect to said cathode, a second source of direct current potential connected to the anode for maintaining the anode at a predetermined positive potential greater than the first-named potential with respect to said cathode, means connected to the accelerating electrode for maintaining the accelerating electrode at a predetermined positive potential with respect to said cathode, means connected to the screen grid for applying a direct current potential of predetermined polarity with respect to the cathode and adjustable amplitude to said screen grid, said suppressor being connected to said cathode,

means connected to said cathode for applying a negative input trigger to said cathode, means connected to the control grid for applying a negative biasing potential of adjustable amplitude to the control grid, a coupling capacitor connecting the dynode to the control grid, and resistance means in the charging path of said coupling capacitor, said secondary emission tube being normally biased to cut-off, said secondary emission tube having a predetermined internal saturated cathode-to-control grid impedance, the application of a negative input trigger to said cathode initiating conduction in said secondary emission tube, electrons from the cathode being attracted to said dynode thereby causing a greater number of electrons to flow from the dynode to the anode, the movement of electrons from the dynode causing the dynode to assume an increased positive potential, said increased positive potential being coupled through the capacitor to the control grid thereby maintaining the secondary emission tube in conduction for a predetermined period of time in accordance with the charging time of the coupling capacitor, the flow of anode current causing the anode to fall in potential thereby producing a negative output pulse in the output circuit means, said resistance means being effectively in parallel with said internal impedance, variations in the direct current potential applied to the screen grid varying the internal impedance of the tube and thereby varying the period of charge of the coupling capacitor between the dynode and the control grid thereby varying the time during which the secondary emission tube is conductive and accordingly varying the width of the output pulse.

11. A variable width pulse generator comprising in combination: a secondary emission tube having a plurality of electrodes including at least an anode, a cathode, a screen grid, a control grid and dynode; means connected to said electrodes for respectively biasing said electrodes; feedback means for connecting a voltage from said dynode to said control grid; and means for varying the internal cathode to control grid impedance of said tube to vary the feedback characteristics of said feedback means.

12. A pulse generator for generating a variable width output signal in response to an input trigger signal, comprising in combination: a secondary emission tube having a plurality of electrodes including at least a cathode, control grid, screen grid, dynode and anode; means connected to said electrodes for biasing said electrodes; variable control means connected to said screen grid for varying the cathode to control grid resistance of said tube; a charging path including resistance means, said cathode to control grid resistance, and feedback means for coupling a voltage at said dynode to said control grid; said resistance means being in shunt relationship with said cathode to control grid resistance whereby the varying of said cathode to control grid resistance varies said charging path; and output means for deriving an output signal in response to said input trigger signal, the width of said output signal being determined by said variable control means.

References Cited in the file of this patent UNITED STATES PATENTS 2,509,998 Van Der Mark et al. May 30, 1950 2,673,331 Liguori Mar. 23, 1954 2,949,578 Narud Aug. 16, 1960 

1. A GATE GENERATOR FOR GENERATING A GATE OF VARIABLE WIDTH COMPRISING, IN COMBINATION, A SECONDARY EMISSION TUBE HAVING AT LEAST A CATHODE, CONTROL GRID, SCREEN GRID, DYNODE AND ANODE, A SOURCE OF A DIRECT CURRENT WIDTH CONTROL POTENTIAL OF UNIFORM POLARITY AND OF VARIABLE AMPLITUDE, CIRCUIT MEANS CONNECTING SAID SOURCE TO SAID SCREEN GRID FOR VARYING THE DIRECT CURRENT POTENTIAL ON THE SCREEN GRID, A SOURCE OF ANODE POTENTIAL OF PREDETERMINED AMPLITUDE, A FIRST RESISTOR, A RECTIFIER, SAID ANODE, SAID FIRST RESISTOR, SAID SOURCE OF ANODE POTENTIAL, SAID RECTIFIER AND SAID CATHODE BEING IN SERIES CIRCUIT RELATIONSHIP, OUTPUT LEAD MEANS CONNECTED TO SAID ANODE, A SOURCE OF TRIGGER PULSES OF PREDETERMINED AMPLITUDE AND POLARITY, FURTHER CIRCUIT MEANS CONNECTING SAID LAST-NAMED SOURCE TO SAID CATHODE, A SOURCE OF DYNODE POTENTIAL, MEANS INCLUDING A SECOND RESISTOR CONNECTING SAID SOURCE OF DYNODE POTENTIAL TO SAID DYNODE, A FEEDBACK CAPACITOR OPERATIVELY CONNECTING SAID DYNODE TO SAID CONTROL GRID, A SOURCE OF CONTROL GRID BIASING POTENTIAL, AND MEANS INCLUDING A THIRD RESISTOR CONNECTING SAID SOURCE OF BIASING POTENTIAL TO SAID CONTROL GRID, SAID SECONDARY EMISSION TUBE NORMALLY IN THE ABSENCE OF AN INPUT TRIGGER APPLIED TO SAID CATHODE BEING BIASED AT CUT-OFF BY THE BIASING POTENTIAL APPLIED TO THE CONTROL GRID, A TRIGGER PULSE OF PREDETERMINED POLARITY APPLIED TO SAID CATHODE INITIATING ELECTRON FLOW IN SAID SECONDARY EMISSION TUBE FROM SAID CATHODE TO SAID DYNODE, SECONDARY EMISSION FROM THE DYNODE TO THE ANODE CONSISTING OF A LARGER NUMBER OF ELECTRONS THAN REACH SAID DYNODE FROM SAID CATHODE WHEREBY SAID DYNODE ASSUMES AN INCREASED POSITIVE POTENTIAL, SAID INCREASED POSITIVE POTENTIAL BEING APPLIED THROUGH SAID FEEDBACK CAPACITOR TO SAID CONTROL GRID, THE ELECTRON FLOW FROM SAID DYNODE AND CATHODE TO SAID ANODE CAUSING A CURRENT FLOW IN SAID FIRST RESISTOR THEREBY REDUCING THE POTENTIAL ON SAID ANODE AND CAUSING AN OUTPUT GATE PULSE OF NEGATIVE POLARITY ON THE OUTPUT LEAD MEANS, SAID THIRD RESISTOR IN SAID CONTROL GRID CIRCUIT BEING SELECTED IN VALUE IN ACCORDANCE WITH THE INTERELECTRODE RESISTANCE BETWEEN THE CATHODE AND CONTROL GRID OF SAID SECONDARY EMISSION TUBE WHEREBY SAID THIRD RESISTOR IS SUBSTANTIALLY GREATER THAN SAID INTERELECTRODE RESISTANCE THEREBY PROVIDING THAT THE RESISTANCE IN THE CHARGING PATH OF SAID FEEDBACK CAPACITOR IS A LINEAR FUNCTION OF THE DIRECT CURRENT POTENTIAL ON THE SCREEN GRID, AN INCREASE IN THE POSITIVE DIRECT CURRENT POTENTIAL ON THE SCREEN GRID WITH RESPECT TO THE CATHODE ACCELERATING ELECTRONS WHICH PASS THE CONTROL GRID TO A HIGHER VELOCITY WHEREBY FEWER ELECTRONS ARE COLLECTED BY THE CONTROL GRID AND THE SATURATED CATHODE-TO-CONTROL-GRID RESISTANCE OF THE SECONDARY EMISSION TUBE IS INCREASED RESULTING IN A LONGER CHARGING TIME FOR THE FEEDBACK CAPACITOR AND A WIDER OUTPUT GATE WIDTH, A DECREASE IN SAID DIRECT CURRENT POTENTIAL ON THE SCREEN GRID RESULTING IN A NARROWER OUTPUT GATE WIDTH. 